1. Field of the Invention
The present invention relates to an equatorial sundial, and more particularly to a new and novel equatorial sundial with an adjustable base assembly that uses one or more concave cylindrical focusing mirrors to form a sharply demarcated beam of light either upon opaque or multi-faced translucent surfaces, to accurately tell time in a variety of geometric and aesthetic configurations.
2. Description of the Prior Art
Equatorial sundials have been known in the prior art for centuries. Most types of equatorial sundials cast a shadow from a gnomon forming a line upon a surface where the time is then read. The prior art also includes equatorial sundials which instead reflect or project unfocused light to indicate the time. These have included a masked reflecting mirror to cast a darkened line from the masking upon the dial as in U.S. Pat. No. 3,786,570 Davies; a reflected spot of light projected upon a translucent elliptical surface as in U.S. Pat. No. 5,197,199 Shrader; and a sunbeam that enters a hole in the top of a translucent sphere which casts a spot on the inside of the sphere allowing time to be read on the external surface of the device as in U.S. Pat. No. 89,585 Johnson. The limitations known in the prior art utilizing shadows is that they inherently form indistinct demarcations of time because of the penumbra the shadow creates and therefore these types of sundials are not able to give sharply defined demarcations for telling of time in a more precise manner.
The limitations known in the prior art with reflected un-focused light is that the width of the resultant image is blurred because it equals the width of the sun's image plus the width of the mirror. Each of the aforementioned sundials require a broad field or screen for the time to be displayed since each relies upon one light directing or shadow directing component of the device to function throughout the sun's total traverse across the horizon. This breadth of field or screen and lack of a sharply focused demarcation from the sun makes the reading of time from the sundial more difficult and in some instances requiring a modicum of study to discern the time.
A further limitation in the prior art is the difficulty in setting up and properly aligning the sundial accurately in accordance with the latitude where the sundial is located. The present invention utilizes an adjustable base assembly that permits a user to set up the sundial with exceptional accuracy.
Given the limitations of the prior art there is an apparent need for an equatorial sundial with an adjustable base assembly that utilizes a reflective means whereby the time indicator will be sharply focused and the visual field or screen of the time indicator may be narrowed, thereby making the dial easier to be read. The prior art's single component shadowing or reflecting time indicator source also limits the geometric and aesthetic configurations of sundials utilizing these designs. In this respect, the present invention disclosed herein substantially fulfills these needs.